Add some content into the _targets.rst file

[felixfontein]

Should fix https://github.com/ansible-collections/community.general/runs/7003212532?check_suite_focus=true, which fails because of

  /home/runner/work/_temp/docsbuild/base/rst/_targets.rst:2: WARNING: Field list ends without a blank line; unexpected unindent.
  /home/runner/work/_temp/docsbuild/base/rst/_targets.rst:30: WARNING: malformed hyperlink target.
  /home/runner/work/_temp/docsbuild/base/rst/_targets.rst:31: WARNING: Explicit markup ends without a blank line; unexpected unindent.  

[briantist]

Is there a simple "rst validator" or something we could add to the CI? 🤔

[felixfontein]

There's rstcheck: https://pypi.org/project/rstcheck/

[felixfontein]

I've tried adding this in #51